Re: [PATCH V9 23/24] arm64: dts: allwinner: rg35xx: Add GPIO backlight control

[Andre Przywara <andre.przywara@arm.com>]

On Wed,  7 May 2025 15:19:42 -0500
Chris Morgan <macroalpha82@gmail.com> wrote:

Hi Chris,

> From: Chris Morgan <macromorgan@hotmail.com>
> 
> The LCD backlight for this device can be exposed as a simple GPIO-
> controlled device. It would be more accurately modelled using PWM to
> enable brightness control, however the PWM driver design for the H616 is
> not yet upstreamed.

I don't think this is right then: First there should be no notion of a
"driver being upstreamed" in a *DT* patch, as "the driver" is a Linux
speciality, which the DT itself doesn't care about.
And secondly we should not chicken out and go with an interim solution.

So I guess we need to wait for the PWM binding to appear.

Cheers,
Andre

> Add a GPIO backlight node to the DTS.
> 
> Signed-off-by: Ryan Walklin <ryan@testtoast.com>
> Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
> ---
>  .../boot/dts/allwinner/sun50i-h700-anbernic-rg35xx-2024.dts | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/allwinner/sun50i-h700-anbernic-rg35xx-2024.dts b/arch/arm64/boot/dts/allwinner/sun50i-h700-anbernic-rg35xx-2024.dts
> index 7e17ca07892d..95f2ae04bd95 100644
> --- a/arch/arm64/boot/dts/allwinner/sun50i-h700-anbernic-rg35xx-2024.dts
> +++ b/arch/arm64/boot/dts/allwinner/sun50i-h700-anbernic-rg35xx-2024.dts
> @@ -21,6 +21,12 @@ aliases {
>  		serial0 = &uart0;
>  	};
>  
> +	backlight: backlight {
> +		compatible = "gpio-backlight";
> +		gpios = <&pio 3 28 GPIO_ACTIVE_HIGH>; // PD28
> +		default-on;
> +	};
> +
>  	battery: battery {
>  		compatible = "simple-battery";
>  		constant-charge-current-max-microamp = <1024000>;